1. Field of the Invention
The present invention relates to laminate film packaged storage devices and methods of fabricating the same, in particular to laminate film packaged storage devices, such as batteries and electric double layer capacitors whose sealing properties and a volume efficiency are improved, and methods of fabricating the same.
2. Description of the Related Art
In recent years, in the field of information and communications, smaller size and lighter weight tendency of portable devices has been advanced. In accordance with this tendency, storage devices such as batteries and electric double layer capacitors are smaller in size, lighter in weight and capable of more rapidly charging and discharging, and are in active development.
As a solution for the smaller size and lighter weight storage devices, it is proposed that a laminate film is formed by that a layer of polymer molecule film and a layer of metal foil are laminated and is used as a packaging material. Furthermore, in order to improve rapid charge and discharge properties, as a terminal, use is made of a plate of metal, such as copper small in conductive resistance. For instance, in JP-B-62-8932 (hereinafter referred to as a first existing technology), an electric double layer capacitor is proposed in which an opening is made in a polypropylene film of a laminate film and a layer of metal foil, for example aluminum, is exposed, the exposed layer of metal foil is brought into contact with a carbon electrode, and thereby forming an external terminal.
In the first existing technology, a problem exists that it is difficult to remove the polypropylene film alone although the volume efficiency of the electric double layer capacitor can be improved. Another problem exists that since the package is partially formed only of the aluminum foil, mechanical strength thereof is weak. In the above first existing technology, still another problem exists that because of the aluminum foil coming into contact with an electrolytic solution, the aluminum foil is eaten away with the electrolytic solution.
JP-A-2-94619 (a second existing technology) discloses a method of fabricating the electric double layer capacitors that enables improving the above first existing technology. In this technology, first, a polarizable electrode and a collector are integrally bonded with a conductive adhesive. In another process, a laminate film with a window is prepared. Against the window of the laminate film, the integrally bonded polarizable electrode and collector are disposed and appropriately temporarily bonded thereto followed by immersing in an electrolytic solution bath to impregnate the electrolytic solution, thereafter the laminate films are closely brought into contact.
In the existing second technology, in a separate process the opening is made in the laminate film, this laminate film is stuck to the polarizable electrode and collector that are integrally bonded with the conductive adhesive. Accordingly, the problems in the first existing technology can be overcome. However, another problem exists that since the electrolytic solution penetrates into between the collector and the laminate film, the collector and the laminate film cannot be brought into close contact.
It is an object of the present invention to provide laminate film packaged storage devices that can overcome the above problems of the existing technology and improve sealing properties and volume efficiency. It is another object of the present invention to provide methods of fabricating the laminate film packaged storage devices.
According to the present invention, there is provided a laminate film packaged storage device which includes a fundamental cell that is constituted by disposing a positive electrode layer and a negative electrode layer, respectively, on both surfaces of a separator, a first structure that is constituted by disposing a first laminate film having a first opening and a first collector rubber with a first metal terminal plate interposed therebetween and in which a first collector rubber surface is disposed so as to come into contact with a surface of the positive electrode layer of the fundamental cell, and a second structure that is constituted by disposing a second laminate film having a second opening and a second collector rubber with a second metal terminal plate interposed therebetween and in which a second collector rubber surface is disposed so as to come into contact with a surface of the negative electrode layer of the fundamental cell. In the above, the fundamental cell is sealed off in a package cell made of the first structure and the second structure by fusion bonding the first laminate film and the second laminate film at the peripheries thereof, and the first and second metal terminal plates, respectively, are partially exposed at the first and second openings.
In the above configuration of the laminate film packaged storage device of the present invention, the first laminate film is fusion bonded to the first metal terminal plate and the first collector rubber, and the second laminate film is fusion bonded to the second metal terminal plate and the second collector rubber. That is, each of the metal terminal plates is preferable to be surrounded by the corresponding laminate film and collector rubber.
In the above configuration of the laminate film packaged storage device of the present invention, surfaces of the first and second metal terminal plates exposed at the first and second openings are preferably used as terminals for use in external connection.
According to the present invention, there is provided a method of fabricating a laminate film packaged storage device which includes the steps of preparing a structure by disposing a collector rubber on the laminate film so as to cover the metal terminal plate followed by fusion bonding the metal terminal plate and the collector rubber onto the laminate film after a metal terminal plate is disposed on a laminate film having an opening so as to cover the opening thereof, disposing the structure on each of a positive electrode layer and a negative electrode layer of a fundamental cell that is constituted by sandwiching both surfaces of a separator, respectively, with the positive electrode layer and the negative electrode layer so that surfaces of the collector rubbers face each other, and fusion bonding two of the structures at peripheries thereof, and thereby sealing off the fundamental cell in a package cell.
In a laminate film packaged storage device of the present invention, since the metal terminal plate is surrounded by the laminate film and the collector rubber, the metal terminal plate is not eaten away with the electrolytic solution and the electrolytic solution can be hindered from leaking. Furthermore, since the laminate film is processed so as to have a partial opening and the metal terminal plate exposed in the opening can be used as an external connection terminal, a volume efficiency of the laminate film packaged storage device can be improved.